Could this be a correct definition of potency?

[LeonardDeNoblac]

Everyone who is familiar with Aristotelian/Thomist metaphysics (as every learned Catholic, I think) knows what is meant by potency and act. What I was thinking about is: if the act can be defined as the realization of the potency, can we define potency (among other definitions) as the lack of act (for example, as cold can be definied as the lack of heat, darkness can be defined as the lack of light and evil can be defined as the lack of good)? Or is there anything erroneous in this definition?

 

[Gorgias]

if the act can be defined as the realization of the potency, can we define potency (among other definitions) as the lack of act

I think I see what you’re trying to get at. However, I don’t think that would be a helpful definition. After all, cold does not lead to heat, nor darkness light, nor evil good. However, potency is all about the ability for actualization to take place.

 

[rom]

In the language of Aristotle and St. Thomas the lack of act would be the definition of “privation,” which is one of the three physical principles of generation.

The physical principles of a thing in its state of actual existence are two in number: subject and form. What is known as prime matter is the first substantial subject from which every mobile (changeable) being is made.

The physical principles of a thing in its state of becoming or generation, are three in number: subject, form and privation.

 

[rom]

Strictly speaking, neither act nor potency can be properly defined because they are first principles of being. They do not have a proper genus nor a proper differentia. However, they can be described.

The notion of act can only be derived from examples. For example, we say that a thing is in act when it exists, or when it exercises its own existence. A person is in the act of seeing when he or she has the perfection of vision. Thus, act may also be described as perfection.

Potency is best described in relation to act. Potency is the capacity for act.

While potency can be described in relation to act, act cannot be described in relation to potency. Because the first thing known by the intellect is a being-in-act, a being in the act of existing, or an intelligible reality. And we derive the concept of being-in-potency only from the concept of being-in-act.

Between actual being and mere nothing there is a real entity, called potency. Potency is not like privation, which is the simple lack or absence of act. Unlike privation, potency is a possible being in act, whereas a privation is not. For example, blindness is a privation, and doesn’t have any reality except in the mind. It is just a being of reason. On the other hand, prime matter, which is a pure potency, exists in real substances in the world. The latent capacity of material substances to change into a different substance IS its prime matter. This latent capacity is real. Therefore, prime matter is real, but it cannot exist apart from the substance.

Prime matter cannot exist without form because, as pure potency, it is an indeterminate being. But nothing in the world exists indeterminately. Everything that actually exists must exist as a determinate kind of being. Therefore, there is no such thing as pure prime matter or pure potency without form in the world. Prime matter can only exist as co-principle with substantial form in a material substance.